DUV LASER ANNEALING AND STABILIZATION OF SiCOH FILMS

ABSTRACT

A method of fabricating a dielectric film comprising atoms of Si, C, O and H (hereinafter SiCOH) that has improved insulating properties as compared with prior art dielectric films, including prior art SiCOH dielectric films that are not subjected to the inventive deep ultra-violet (DUV) is disclosed. The improved properties include reduced current leakage which is achieved without adversely affecting (increasing) the dielectric constant of the SiCOH dielectric film. In accordance with the present invention, a SiCOH dielectric film exhibiting reduced current leakage and improved reliability is obtained by subjecting an as deposited SiCOH dielectric film to a DUV laser anneal. The DUV laser anneal step of the present invention likely removes the weakly bonded C from the film, thus improving leakage current.

RELATED APPLICATION

This application is a divisional application of U.S. Ser. No.10/923,247, filed Aug. 20, 2004.

FIELD OF THE INVENTION

The present invention relates to a method of fabricating a dielectricfilm for use in semiconductor applications such as BEOL(back-end-of-the-line) applications, and more particularly to a methodof fabricating a dielectric film comprising Si, C, O and H atoms (hereinafter “SiCOH”), also called C doped oxide (CDO), that has a lowdielectric constant (k), improved leakage current and improved filmreliability. The present invention also relates to the dielectric filmthat is fabricated using the method of the present invention as well aselectronic structures, such as interconnect structures, that include theinventive dielectric film.

BACKGROUND OF THE INVENTION

The continuous shrinking in dimensions of electronic devices utilized inULSI (ultra large scale integration) circuits in recent years hasresulted in increasing the resistance of the BEOL metallization as wellas increasing the capacitance of the intralayer and interlayerdielectric. This combined effect increases signal delays in ULSIelectronic devices. In order to improve the switching performance offuture ULSI circuits, low dielectric constant (k) insulators andparticularly those with k significantly lower than silicon oxide areneeded to reduce the capacitances. Dielectric materials (i.e.,dielectrics) that have low k values are commercially available. One suchcommercially available material, for example, is polytetrafluoroethylene(“PTFE”), which has a dielectric constant of about 2.0. Mostcommercially available dielectric materials however are not thermallystable when exposed to temperatures above 300° C. Integration of low kdielectrics in present ULSI chips requires a thermal stability of atleast 400° C.

The low k materials that have been considered for applications in ULSIdevices include polymers containing atoms of Si, C, O and H, such asmethylsiloxane, methylsilsesquioxanes, and other organic and inorganicpolymers. For instance, a paper (N. Hacker et al. “Properties of new lowdielectric constant spin-on silicon oxide based dielectrics” Mat. Res.Soc. Symp. Proc. 476 (1997): 25) describes materials that appear tosatisfy the thermal stability requirement, even though some of thesematerials propagate cracks easily when reaching thicknesses needed forintegration in an interconnect structure when films are prepared by aspin-on technique. Furthermore, these prior art precursor materials arehigh cost and prohibitive for use in mass production. Moreover, most ofthe fabrication steps of very-large-scale-integration (“VLSI”) and ULSIchips are carried out by plasma enhanced chemical or physical vapordeposition techniques.

The ability to fabricate a low k material by a plasma enhanced chemicalvapor deposition (PECVD) technique using previously installed andavailable processing equipment will thus simplify its integration in themanufacturing process, reduce manufacturing cost, and create lesshazardous waste. U.S. Pat. Nos. 6,147,009 and 6,497,963 describe a lowdielectric constant material consisting of atoms of Si, C, O and Hhaving a dielectric constant not more than 3.6 and which exhibits verylow crack propagation velocities.

U.S. Pat. Nos. 6,312,793, 6,441,491, 6,541,398 and 6,479,110 B2 describea multiphase low k dielectric material that consists of a matrix phasecomposed of atoms of Si, C, O and H and another phase composed mainly ofC and H. The dielectric materials disclosed in the foregoing patentshave a dielectric constant of not more than 3.2.

U.S. Pat. No. 6,437,443 describes a low k dielectric material that hastwo or more phases wherein the first phase is formed of a SiCOHmaterial. The low k dielectric material is provided by reacting a firstprecursor gas containing atoms of Si, C, O, and H and at least a secondprecursor gas containing mainly atoms of C, H, and optionally F, N and Oin a plasma enhanced chemical vapor deposition chamber.

Despite the numerous disclosures of methods of fabricating low k SiCOHdielectric films, the prior art SiCOH films contain a high content of Catoms (typically about 10-20 atomic % or greater) that increase theleakage currents of the device containing the SiCOH film. The increasein leakage current, in turn, degrades the insulating property of thefilm and therefore adversely effects the films reliability. Thus, thereis a need for providing SiCOH films that have improved leakage currentusing a method that does not effect the dielectric constant and/or thereliability of the SiCOH film.

SUMMARY OF THE INVENTION

The present invention provides a method of fabricating a SiCOHdielectric film that has improved insulating properties as compared withprior art dielectric films, including prior art SiCOH dielectric filmsthat are not subjected to the inventive deep ultra-violet (DUV) laseranneal. The improved properties include reduced current leakage which isachieved without adversely effecting (increasing) the dielectricconstant of the SiCOH dielectric film. In accordance with the presentinvention, a SiCOH dielectric film exhibiting reduced current leakageand improved reliability is obtained by subjecting an as deposited SiCOHdielectric film to a DUV laser anneal step. It is the applicants' beliefthat the DUV laser anneal step of the present invention likely removesthe weakly bonded C from the film, thus improving leakage current.

Electron beam is currently used to stabilize many dielectric filmsincluding SiCOH dielectric films. The drawback of using electron beamtreatment is that weakly bonded C is not typically removed from the filmand the introduced electrons may cause unwanted changes to the film.High temperature annealing (on the order of about 500° C. to about 600°C.) also does not typically remove C and thus cannot stabilize the film.A photoreaction between C atoms and deep UV is needed to improve thequality of the SiCOH dielectric film.

In broad terms, the method of the present invention comprises the stepsof:

-   -   providing a dielectric film comprising atoms of Si, C, O and H        on a surface of a substrate; and    -   irradiating said dielectric film using a deep ultra-violet (DUV)        laser to cause a photochemical reaction within the dielectric        film which improves the insulating properties of the film as        compared with a non-DUV laser treated SiCOH film.

In addition to the method described above, the present invention alsoprovides a SiCOH dielectric film which has improved insulatingproperties, i.e., reduced leakage current, as compared with a non-DUVtreated SiCOH film.

In broad terms, the inventive dielectric film of the present inventioncomprises a dielectric material comprising atoms of Si, C, O and H, saiddielectric material having a covalently bonded tri-dimensional networkstructure, a dielectric constant of not more than 2.8 and a reflectancespectra that is substantially equivalent to SiO₂.

By “substantially equivalent to SiO₂” it is meant that the SiCOHdielectric film has about 60% reflectance at DUV (248 nm) typical ofSiO₂ as shown in FIG. 6, where the SiO₂ and laser annealed SiCOH filmshave about the same reflectance spectra. For an unexposed SiCOH film,the reflectance at DUV is low (approximately 20%) indicating absorptiondue to C atoms.

As stated above, the inventive DUV treated SiCOH dielectric film hasimproved insulating properties as compared to a non-DUV treated SiCOHdielectric film. The improved insulating properties include reducedleakage current that is observed when the inventive films are used inelectronic structures. In particular, the inventive DUV laser treatedSiCOH dielectric film has a current density at least one to severalorders of magnitude less leakage current as compared to a non-DUV laser(i.e., as deposited) SiCOH dielectric. This is shown in FIG. 8 where a Crich SiCOH film has very high leakage currents as deposited (off-scalein FIG. 8) and after laser anneal leakage currents are greatly reducedat about 10⁻⁷ A/cm² at −2V. The reflectance spectra for this particularsample is shown in FIG. 7. Before laser annealing, the SiCOH film has alow reflectance (approximately 15%) at DUV (curve C), and, after laserannealing, the reflectance is about 60% at DUV, which is typical of SiO₂films (curve D).

The present invention also relates to electronic structures that includeat least one insulating material that comprises the inventive DUV lasertreated SiCOH dielectric film of the present invention. The at least onedielectric film comprising the inventive DUV laser treated SiCOHdielectric may comprise an interlevel and/or intralevel dielectriclayer, a capping layer, and/or a hard mask/polish-stop layer in anelectronic structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B are pictorial representations (through cross sectionalviews) illustrating the basic processing steps of the present invention.

FIG. 2 is an enlarged, cross-sectional view of an electronic device ofthe present invention that includes the inventive DUV laser treatedSiCOH dielectric film as both the intralevel dielectric layer and theinterlevel dielectric layer.

FIG. 3 is an enlarged, cross-sectional view of the electronic structureof FIG. 2 having an additional diffusion barrier dielectric cap layerdeposited on top of the inventive DUV laser treated SiCOH dielectricfilm.

FIG. 4 is an enlarged, cross-sectional view of the electronic structureof FIG. 3 having an additional RIE hard mask/polish-stop dielectric caplayer and a dielectric cap diffusion barrier layer deposited on top ofthe polish-stop layer.

FIG. 5 is an enlarged, cross-sectional view of the electronic structureof FIG. 4 having additional RIE hard mask/polish-stop dielectric layersdeposited on top of the DUV laser treated SiCOH dielectric film of thepresent invention.

FIG. 6 is a plot of reflectance vs. wavelength for various dielectricfilms including SiO₂, SiLK® (a polyarylene ether supplied by The DowChemical Co.), SiCOH without laser treatment, and a DUV laser treatedSiCOH film.

FIG. 7 is a plot of reflectance vs. wavelength for a non-DUV lasertreated SiCOH dielectric film and a DUV laser treated SiCOH dielectricfilm.

FIG. 8 is a graph showing the current-voltage characteristics of a SiCOHfilm before and after DUV laser treatment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention, which describes a method of fabricating a SiCOHdielectric material having improved insulating properties, a DUV lasertreated SiCOH dielectric film and electronic structures containing thesame, will now be described in greater detail. In accordance with themethod of the present invention, a SiCOH dielectric film 12 is formed ona surface of a substrate 10 such as shown, for example, in FIG. 1A. Theterm “substrate” when used in conjunction with substrate 10 includes, asemiconducting material, an insulating material, a conductive materialor any combination thereof, including multilayered structures. Thus, forexample, substrate 10 can be a semiconducting material such as Si, SiGe,SiGeC, SiC, GaAs, InAs, InP and other III/V or II/VI compoundsemiconductors. The semiconductor substrate 10 can also include alayered substrate such as, for example, Si/SiGe, Si/SiC,silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs).When substrate 10 is an insulating material, the insulating material canbe an organic insulator, an inorganic insulator or a combination thereofincluding multilayers. When the substrate 10 is a conductive material,the substrate 10 may include, for example, polySi, an elemental metal,alloys of elemental metals, a metal silicide, a metal nitride andcombinations thereof, including multilayers.

In some embodiments, the substrate 10 includes a combination of asemiconducting material and an insulating material, a combination of asemiconducting material and a conductive material or a combination of asemiconducting material, an insulating material and a conductivematerial. An example of a substrate that includes a combination of theabove is an interconnect structure.

The SiCOH dielectric film 12 is typically deposited using plasmaenhanced chemical vapor deposition (PECVD). In addition to PECVD, thepresent invention also contemplates that the SiCOH dielectric film 12can be formed utilizing chemical vapor deposition (CVD), high-densityplasma (HDP) deposition, pulsed PECVD, spin-on application, or otherrelated methods. The thickness of the dielectric film 12 deposited mayvary; typical ranges for the deposited dielectric film 12 are from about50 nm to about 1 μm, with a thickness from 100 to about 500 nm beingmore typical.

Typically, the SiCOH dielectric film is deposited using the processingtechniques disclosed in co-assigned U.S. Pat. Nos. 6,147,009, 6,312,793,6,441,491, 6,437,443, 6,441,491, 6,541,398, 6,479,110 B2, and 6,497,963,the contents of which are incorporated herein by reference.

Specifically, the SiCOH dielectric film 12 is formed by providing atleast a first precursor (liquid, gas or vapor) comprising atoms of Si,C, O, and H, and an inert carrier such as He or Ar, into a reactor,preferably the reactor is a PECVD reactor, and then depositing a filmderived from said first precursor onto a suitable substrate utilizingconditions that are effective in forming a SiCOH dielectric material.The present invention yet further provides for mixing the firstprecursor with an oxidizing agent such as O₂, CO₂ or a combinationthereof, thereby stabilizing the reactants in the reactor and improvingthe uniformity of the dielectric film 12 deposited on the substrate 10.

In addition to the first precursor, a second precursor (gas, liquid orvapor) comprising atoms of C, H, and optionally O, F and N can be used.Optionally, a third precursor (gas, liquid or gas) comprising Ge mayalso be used.

Preferably, the first precursor is selected from organic molecules withring structures comprising SiCOH components such as1,3,5,7-tetramethylcyclotetrasiloxane (“TMCTS” or “C₄H₁₆O₄Si₄”),octamethylcyclotetrasiloxane (OMCTS), diethoxymethylsilane (DEMS),dimethyldimethoxysilane (DMDMOS), diethylmethoxysilane (DEDMOS), andrelated cyclic and non-cyclic silanes, siloxanes and the like.

The second precursor that may be used is a hydrocarbon molecule.Although any hydrocarbon molecule such as, for example, ethylene may beused, preferably the second precursor is selected from the groupconsisting of hydrocarbon molecules with ring structures, preferablywith more than one ring present in the molecule or with branched chainsattached to the ring. Especially useful, are species containing fusedrings, at least one of which contains a heteroatom, preferentiallyoxygen. Of these species, the most suitable are those that include aring of a size that imparts significant ring strain, namely rings of 3or 4 atoms and/or 7 or more atoms. Particularly attractive, are membersof a class of compounds known as oxabicyclics, such as cyclopenteneoxide (“CPO” or “C₅H₈O”). Also useful are molecules containing branchedtertiary butyl (t-butyl) and isopropyl (i-propyl) groups attached to ahydrocarbon ring; the ring may be saturated or unsaturated (containingC═C double bonds). The third precursor may be formed from germanehydride or any other reactant comprising a source Ge.

The SiCOH film 12 may deposited using a method the includes the step ofproviding a parallel plate reactor, which has a conductive area of asubstrate chuck between about 85 cm² and about 750 cm², and a gapbetween the substrate and a top electrode between about 1 cm and about12 cm. A high frequency RF power is applied to one of the electrodes ata frequency between about 0.45 Mhz and about 200 Mhz. Optionally, anadditional low frequency power can be applied to one of the electrodes.

The conditions used for the deposition step may vary depending on thedesired final dielectric constant of the SiCOH dielectric film 12.Broadly, the conditions used for providing a stable dielectric materialcomprising elements of Si, C, O, H that has a dielectric constant ofabout 2.8 or less include: setting the substrate temperature at betweenabout 300° C. and about 425° C.; setting the high frequency RF powerdensity at between about 0.1 W/cm² and about 1.5 W/cm²; setting thefirst liquid precursor flow rate at between about 100 mg/min and about5000 mg/min, optionally setting the second liquid precursor flow rate atbetween about 50 mg/min to about 10,000 mg/min; optionally setting thethird liquid precursor flow rate at between about 25 mg/min to about4000 mg/min; optionally setting the inert carrier gases such as helium(or/and Argon) flow rate at between about 50 sccm to about 5000 sccm;setting the reactor pressure at a pressure between about 1000 mTorr andabout 7000 mTorr; and setting the high frequency RF power between about75 W and about 1000 W. Optionally, an ultra low frequency power may beadded to the plasma between about 30 W and about 400 W. When theconductive area of the substrate chuck is changed by a factor of X, theRF power applied to the substrate chuck is also changed by a factor ofX.

When an oxidizing agent is employed in the present invention, it isflown into the PECVD reactor at a flow rate between about 10 sccm toabout 1000 sccm.

While liquid precursors are used in the above example, it is known inthe art that the organosilicon gas phase precursors (such astrimethylsilane) can also be used for the deposition. A porogen can beincluded during the deposition of the dielectric film 12 that causessubsequent pore formation within the film 12 during a subsequent curingstep. The subsequent curing step may occur prior to the DUV laser annealstep or curing may occur during the DUV laser anneal step.

The dielectric film 12 formed at this point of the present inventioncontains a matrix of a hydrogenated oxidized silicon carbon material(SiCOH) comprising atoms of Si, C, O and H in a covalently bondedtri-dimensional network and having a dielectric constant of not morethan about 2.8. The tri-bonded network may include a covalently bondedtri-dimensional ring structure comprising Si—O, Si—C, Si—H, C—H and C—Cbonds. The dielectric film 12 may comprise F and N and may optionallyhave the Si atoms partially substituted by Ge atoms. The dielectric film12 may contain molecular scale voids (i.e., nanometer-sized pores) ofbetween about 0.3 to about 50 nanometers in diameter, and mostpreferably between about 0.4 and about 10 nanometers in diameter,further reducing the dielectric constant of the film 12 to values belowabout 2.0. The nanometer-sized pores of film 12 occupy a volume ofbetween about 0.5% and about 50% of a volume of the material. Morepreferably, the dielectric constant of the film 12 is from about 1.6 toabout 2.6, and most preferably from about 1.8 to about 2.2. Theuntreated SiCOH film 12 preferably has a thickness of not more than 1.3micrometers and a crack propagation velocity in water of less than 10⁻⁹meters per second.

The SiCOH dielectric film 12 comprises between about 5 and about 40atomic percent of Si; between about 5 and about 45 atomic percent of C;between 0 and about 50 atomic percent of O; and between about 10 andabout 55 atomic percent of H. The SiCOH dielectric film 12 is thermallystable above 350° C.

Following the deposition of the SiCOH dielectric film 12 onto thesurface of the substrate 10, the resultant structure is irradiatingusing a deep ultra-violet (DUV) laser source so as to provide astructure, such as shown in FIG. 1B, that includes a DUV treated SiCOHdielectric 14 atop the substrate 10. The laser apparatus employed in thepresent invention includes any apparatus that includes a laser that iscapable of lasing DUV radiation. The term “DUV radiation” denotesradiation that has a wavelength below 350 nm. Examples of such laserapparatuses that can be employed in the present invention include thelaser systems depicted in FIGS. 1 and 2 of co-assigned U.S. Pat. No.6,395,650, the entire content of the '650 patent, particularly thedescription of the laser systems, is incorporated herein by reference.

The laser source used to treat the deposited SiCOH dielectric film 12 isan excimer laser which operates at one of several DUV wavelengthsdepending on the laser gas mixture. For example, a XeF laser whichproduces 308 nm radiation can be employed. Also, a KrF laser thatproduces 248 nm radiation, or a ArF laser that produces 193 nm radiationcan be employed in the present invention. Excimer lasers can operate atseveral hundred pulses per second with pulse energies up to a Joule (J)resulting in several hundred Watt (W) output.

The laser employed in treating the deposited SiCOH dielectric film 12preferably operates under a pulse mode. The laser beam can be expandedto expose the entire sample. Alternatively, and for larger samples, thelaser exposure area can be raster scanned across the sample to provideuniform dose. Using excimer laser, the fluence is limited to less than 5mJ/cm² per pulse to ensure ablation will not occur. The short pulseduration of about 10 ns for the excimer laser can cause materialablation at fluence levels greater than 20 mJ/cm². Typically, laserfluence levels of 0.1-5 mJ/cm² per pulse are employed. The total dosecan vary from 1 to 10000 Joules/cm², preferably 500-2000 J/cm². This isachieved by multiple laser pulse exposure. For example, a dose of 1000J/cm² can be obtained using a fluence of 1 mJ/cm² for a duration of 10⁶pulses. Excimer laser normally operates at a few hundreds pulses persecond. Depending of the total dosage required, the overall exposuretime period for the DUV laser treatment for a several seconds to hours.A typical 500 J/cm² dose is achieved in less than 15 min using a 200 Hzlaser operating at a fluence level of 3 mJ/cm² per pulse.

The DUV laser annealed SiCOH film 14 of the present invention is morestable than a non-DUV treated SiCOH film (such as film 12). The DUVtreated SiCOH film 14 of the present invention has a dielectric constantthat is substantially the same as the dielectric constant of the asdeposited SiCOH dielectric film 12. A slight increase or decrease (±0.5)in the dielectric constant from the original value of the as depositedSiCOH film 12 may be seen with the DUV treated films. Thus, the DUVtreated SiCOH film 14 has a dielectric constant of less than 2.8 (±0.5).The DUV treated SiCOH dielectric film 14 also has other characteristics,e.g., a tri-bonded network, porosity, crack velocity, thermal stabilityabove 350° C., etc, that are also similar to the as deposited SiCOHdielectric film 12.

One difference between the DUV treated SiCOH film 14 and the asdeposited film 12 is that a photochemical reaction occurs within thefilm which is believed to remove weakly bonded C from the treated film14. The C content within the DUV laser annealed film 14 is thus slightlyless than the untreated dielectric film 12. A decrease in C contentoccurs in the inventive DUV treated SiCOH dielectric film 14. Thereduction of C content within the DUV treated film 14 provides adielectric film that has a reflectance spectra that is substantially thesame as that of SiO₂ which is indicative that C has been removed fromthe film during the DUV laser treatment. This is clearly shown in FIGS.6 and 7 where reflectance spectra are about 15-20% at DUV for asdeposited films. These low reflectance values are due to C absorption,After laser treatment, SiCOH reflectance spectra are about the same asSiO₂ at DUV indicating that C has been, at least, partly removed.

In some embodiments, the DUV treated dielectric film 14 has a leakagecurrent reduction that is about 10 or more after laser treatment. Theinventive dielectric film 14 also can have a reflectance spectra that ischaracterized as having about 60-70% reflectance at 248 nm.

The SiCOH dielectric film 14 of the present invention may be used as theinterlevel and/or intralevel dielectric, a capping layer, and/or as ahard mask/polish-stop layer in electronic structures.

The electronic structure of the present invention includes apre-processed semiconducting substrate that has a first region of metalembedded in a first layer of insulating material, a first region ofconductor embedded in a second layer of insulating material, the secondlayer of insulating material being in intimate contact with the firstlayer of insulating material, the first region of conductor being inelectrical communication with the first region of metal, and a secondregion of conductor being in electrical communication with the firstregion of conductor and being embedded in a third layer of insulatingmaterial, the third layer of insulating material being in intimatecontact with the second layer of insulating material.

In the above structure, each of the insulating layers can comprise theinventive SiCOH dielectric film 14 that has been treated by DUV laserexposure.

The electronic structure may further include a dielectric cap layersituated in-between the first layer of insulating material and thesecond layer of insulating material, and may further include adielectric cap layer situated in-between the second layer of insulatingmaterial and the third layer of insulating material. The electronicstructure may further include a first dielectric cap layer between thesecond layer of insulating material and the third layer of insulatingmaterial, and a second dielectric cap layer on top of the third layer ofinsulating material.

The dielectric cap material can be selected from silicon oxide, siliconnitride, silicon oxynitride, silicon carbon nitride (SiCN), refractorymetal silicon nitride with the refractory metal being Ta, Zr, Hf or W,silicon carbide, silicon carbo-oxide, carbon doped oxides and theirhydrogenated or nitrided compounds. In some embodiments, the dielectriccap itself can comprise the inventive DUV treated SiCOH dielectricmaterial. The first and the second dielectric cap layers may be selectedfrom the same group of dielectric materials. The first layer ofinsulating material may be silicon oxide or silicon nitride or dopedvarieties of these materials, such as PSG or BPSG.

The electronic structure may further include a diffusion barrier layerof a dielectric material deposited on at least one of the second andthird layer of insulating material. The electronic structure may furtherinclude a dielectric layer on top of the second layer of insulatingmaterial for use as a RIE hard mask/polish-stop layer and a dielectricdiffusion barrier layer on top of the dielectric RIE hardmask/polish-stop layer. The electronic structure may further include afirst dielectric RIE hard mask/polish-stop layer on top of the secondlayer of insulating material, a first dielectric RIE diffusion barrierlayer on top of the first dielectric polish-stop layer a seconddielectric RIE hard mask/polish-stop layer on top of the third layer ofinsulating material, and a second dielectric diffusion barrier layer ontop of the second dielectric polish-stop layer. The dielectric RIE hardmask/polish-stop layer may be comprised of the inventive SiCOHdielectric material as well.

The electronic devices which can contain the inventive DUV laser treatedSiCOH dielectric film are shown in FIGS. 2-5. It should be noted thatthe devices shown in FIGS. 2-5 are merely illustrative examples of thepresent invention, while an infinite number of other devices may also beformed by the present invention novel methods.

In FIG. 2, an electronic device 30 built on a semiconductor substrate 32is shown. On top of the semiconductor substrate 32, an insulatingmaterial layer 34 is first formed with a first region of metal 36embedded therein. After a CMP process is conducted on the first regionof metal 36, a DUV laser treated SiCOH dielectric film 38 of the presentinvention is formed on top of the first layer of insulating material 34and the first region of metal 36. The first layer of insulating material34 may be suitably formed of silicon oxide, silicon nitride, dopedvarieties of these materials, or any other suitable insulatingmaterials. The DUV laser treated SiCOH dielectric film 38 is thenpatterned in a photolithography process followed by etching and aconductor layer 40 is deposited thereon. After a CMP process on thefirst conductor layer 40 is carried out, a second layer of the inventiveDUV laser treated SiCOH film 44 is deposited by a plasma enhancedchemical vapor deposition process overlying the first DUV laser treatedSiCOH dielectric film 38 and the first conductor layer 40. The conductorlayer 40 may be a deposit of a metallic material or a nonmetallicconductive material. For instance, a metallic material of aluminum orcopper, or a nonmetallic material of nitride or polysilicon. The firstconductor 40 is in electrical communication with the first region ofmetal 36.

A second region of conductor 50 is then formed after a photolithographicprocess on the DUV laser treated SiCOH dielectric film 44, followed byetching and then a deposition process for the second conductor material.The second region of conductor 50 may also be a deposit of either ametallic material or a nonmetallic material, similar to that used indepositing the first conductor layer 40. The second region of conductor50 is in electrical communication with the first region of conductor 40and is embedded in the second layer of the DUV laser treated SiCOHdielectric film 44. The second layer of the DUV laser treated SiCOHdielectric film 44 is in intimate contact with the first layer of theDUV laser treated SiCOH dielectric material 38. In this example, thefirst layer of the DUV laser treated SiCOH dielectric film 38 is anintralevel dielectric material, while the second layer of the DUV lasertreated SiCOH dielectric film 44 is both an intralevel and an interleveldielectric. Based on properties of the inventive DUV laser treated SiCOHdielectric films, superior insulating property can be achieved by thefirst insulating layer 38 and the second insulating layer 44.

FIG. 3 shows a present invention electronic device 60 similar to that ofelectronic device 30 shown in FIG. 2, but with an additional dielectriccap layer 62 deposited between the first insulating material layer 38and the second insulating material layer 44. The dielectric cap layer 62can be suitably formed of a material such as silicon oxide, siliconnitride, silicon oxynitride, refractory metal silicon nitride with therefractory metal being Ta, Zr, Hf or W, silicon carbide, siliconcarbo-nitride (SiCN), silicon carbo-oxide (SiCO), and their hydrogenatedcompounds. The additional dielectric cap layer 62 functions as adiffusion barrier layer for preventing diffusion of the first conductorlayer 40 into the second insulating material layer 44 or into the lowerlayers, especially into layers 34 and 32.

Another alternate embodiment of the present invention electronic device70 is shown in FIG. 4. In the electronic device 70, two additionaldielectric cap layers 72 and 74 which act as a RIE mask and CMP(chemical mechanical polishing) polish stop layer are used. The firstdielectric cap layer 72 is deposited on top of the first DUV lasertreated SiCOH dielectric material 38 and used as a RIE mask and CMPstop, so the first conductor layer 40 and layer 72 are approximatelyco-planar after CMP. The function of the second dielectric layer 74 issimilar to layer 72, however layer 74 is utilized in planarizing thesecond conductor layer 50. The polish stop layer 74 can be a deposit ofa suitable dielectric material such as silicon oxide, silicon nitride,silicon oxynitride, refractory metal silicon nitride with the refractorymetal being Ta, Zr, Hf or W, silicon carbide, silicon carbo-oxide(SiCO), and their hydrogenated compounds. A preferred polish stop layercomposition is SiCH or SiCOH for layers 72 or 74. When layer 72 iscomprised of SiCOH, it is preferred that the inventive DUV laser treatedSiCOH film be employed. A second dielectric layer 74 can be added on topof the second DUV laser treated SiCOH dielectric film 44 for the samepurposes.

Still another alternate embodiment of the present invention electronicdevice 80 is shown in FIG. 5. In this alternate embodiment, anadditional layer 82 of dielectric material is deposited and thusdividing the second insulating material layer 44 into two separatelayers 84 and 86. The intralevel and interlevel dielectric layer 44formed of the inventive DUV laser treated SiCOH dielectric film, shownin FIG. 2, is therefore divided into an interlayer dielectric layer 84and an intralevel dielectric layer 86 at the boundary between via 92 andinterconnect 94. An additional diffusion barrier layer 96 is furtherdeposited on top of the upper dielectric layer 74. The additionalbenefit provided by this alternate embodiment electronic structure 80 isthat dielectric layer 82 acts as an RIE etch stop providing superiorinterconnect depth control. Thus, the composition of layer 82 isselected to provide etch selectivity with respect to layer 86.

Still other alternate embodiments may include an electronic structurewhich has layers of insulating material as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate which has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of the insulating material wherein the second layer ofinsulating material is in intimate contact with the first layer ofinsulating material, and the first region of conductor is in electricalcommunication with the first region of metal, a second region ofconductor in electrical communication with the first region of conductorand is embedded in a third layer of insulating material, wherein thethird layer of insulating material is in intimate contact with thesecond layer of insulating material, a first dielectric cap layerbetween the second layer of insulating material and the third layer ofinsulating material and a second dielectric cap layer on top of thethird layer of insulating material, wherein the first and the seconddielectric cap layers are formed of a material that includes theinventive DUV laser treated SiCOH dielectric film.

Still other alternate embodiments of the present invention include anelectronic structure which has layers of insulating material asintralevel or interlevel dielectrics in a wiring structure that includesa pre-processed semiconducting substrate that has a first region ofmetal embedded in a first layer of insulating material, a first regionof conductor embedded in a second layer of insulating material which isin intimate contact with the first layer of insulating material, thefirst region of conductor is in electrical communication with the firstregion of metal, a second region of conductor that is in electricalcommunication with the first region of conductor and is embedded in athird layer of insulating material, the third layer of insulatingmaterial is in intimate contact with the second layer of insulatingmaterial, and a diffusion barrier layer comprise the DUV laser treatedSiCOH film of the present invention formed on at least one of the secondand third layers of insulating material.

Still other alternate embodiments include an electronic structure whichhas layers of insulating material as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate that has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of insulating material which is in intimate contactwith the first layer of insulating material, the first region ofconductor is in electrical communication with the first region of metal,a second region of conductor in electrical communication with the firstregion of conductor and is embedded in a third layer of insulatingmaterial, the third layer of insulating material is in intimate contactwith the second layer of insulating material, a reactive ion etching(RIE) hard mask/polish stop layer on top of the second layer ofinsulating material, and a diffusion barrier layer on top of the RIEhard mask/polish stop layer, wherein the RIE hard mask/polish stop layerand the diffusion barrier layer comprise the DUV laser treated SiCOHdielectric film of the present invention.

Still other alternate embodiments include an electronic structure whichhas layers of insulating materials as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate that has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of insulating material which is in intimate contactwith the first layer of insulating material, the first region ofconductor is in electrical communication with the first region of metal,a second region of conductor in electrical communication with the firstregion of conductor and is embedded in a third layer of insulatingmaterial, the third layer of insulating material is in intimate contactwith the second layer of insulating material, a first RIE hard mask,polish stop layer on top of the second layer of insulating material, afirst diffusion barrier layer on top of the first RIE hard mask/polishstop layer, a second RIE hard mask/polish stop layer on top of the thirdlayer of insulating material, and a second diffusion barrier layer ontop of the second RIE hard mask/polish stop layer, wherein the RIE hardmask/polish stop layers and the diffusion barrier layers comprise lasertreated SiCOH dielectric film of the present invention.

Still other alternate embodiments of the present invention includes anelectronic structure that has layers of insulating material asintralevel or interlevel dielectrics in a wiring structure similar tothat described immediately above but further includes a dielectric caplayer which comprises the DUV laser treated SiCOH dielectric material ofthe present invention situated between an interlevel dielectric layerand an intralevel dielectric layer.

The following example is provided to illustrate the method of thepresent invention and to demonstrate some advantages of the resultantDUV laser treated SiCOH dielectric film.

EXAMPLE

In this example, various dielectric films were deposited on a substrateand the reflectance spectra of each of the dielectric films wereobtained by using an n&k analyzer by n&k Technology (Santa Clara,Calif.). The resultant reflectance spectra (reflectance vs. wavelengthin nm) are shown in FIG. 6. The samples including a SiLK® film (Curve A,segmented line), an as deposited SiCOH dielectric (Curve C, solid line)and a DUV treated SiCOH dielectric film (Curve D, solid and bolded line)are compared with an SiO₂ simulated spectra (Curve B, dotted line).

The sample including the SiLK® film was prepared by spin-on coating a500 nm layer of SiLK® onto a Si substrate. The SiO₂ sample was simulatedusing the internal film library supplied with the n&k tool manufacturer.The untreated SiCOH containing sample of FIG. 6 was prepared by PECVD ofTMCTS. The resultant non-DUV laser treated SiCOH film had an asdeposited thickness of about 400 nm. The same film was subjected tolaser treatment using a 248 nm laser source. The conditions for thelaser anneal were as follows: 30 J/min for a total dose of 1800 J.

The reflectance spectrum shown in FIG. 6 illustrated that the SiLK®(curve A) film which had a high C content exhibited low reflectance ofabout 10% at DUV compared with approximately 30% for an untreated SiCOHfilm (Curve C, solid line). As stated before, the higher the C contentin the films, the higher is the absorption (low reflectance). Afterlaser treatment the SiCOH film (Curve D, solid and bolded line)exhibited a reflectance spectra similar to SiO₂ (about 60% reflectanceat DUV, Curve B, dotted line) indicating that the C content had beengreatly reduced.

FIG. 7 shows a simplified spectrum containing only the non-DUV treatedSiCOH dielectric film (Curve C) and the DUV laser treated SiCOH film(Curve D). In this case, the film was deposited by PECVD at 20 mTorrusing TMCTS (flow rate 100 sccm) and 10% acetylene in He (flow rate 40sccm) as the precursors. The acetylene was added to increase the carboncontent to the SiCOH film. Film thickness was about 150 nm. Again, here,as shown before, the as deposited SiCOH film had a reflectance spectraof about 15% at DUV which is lower than 30% for the SICOH film of FIG.6. This is due to the increased C content for the film shown in FIG. 7.After approximately 5 kJ laser treatment the reflectance spectra wasabout 60% at DUV typical of SiO₂ showing again C removal (FIG. 7, curveD). The current-voltage characteristics for the same samples of FIG. 7are shown in FIG. 8. Note that before laser treatment at −2V leakagecurrent is very high and off-scale (curve C). After laser treatmentleakage current is about 10⁻⁷ A/cm² at −2V, decreasing by several ordersof magnitudes as compared with the untreated sample. This again showsthat C removal is important is achieving low leakage currents.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

1. A dielectric film comprising a dielectric material comprising atomsof Si, C, O and H, said dielectric material having a covalently bondedtri-dimensional network structure, a dielectric constant of not morethan 2.8 and an absorption spectra that is substantially equivalent toSiO₂.
 2. The dielectric film of claim 1 wherein said covalently bondedtri-dimensional network structure comprises Si—O, Si—C, Si—H, C—H andC—C bonds.
 3. The dielectric film of claim 1 wherein said dielectricmaterial comprises molecular scale voids of between 0.3 and 50 nm indiameter.
 4. The dielectric film of claim 3 wherein said molecular voidsoccupy a volume between 0.5% and about 50%.
 5. The dielectric film ofclaim 1 wherein said dielectric material comprises a crack propagationvelocity in water of less than 10⁻⁹ meters per second.
 6. The dielectricfilm of claim 1 further comprising an underlying substrate.
 7. Thedielectric film of claim 6 wherein said underlying substrate comprises asemiconducting material, an insulating material, a conductive materialor a combination, including multilayers thereof.
 8. The dielectric filmof claim 7 wherein said underlying substrate comprises a semiconductingmaterial.
 9. The dielectric film of claim 1 wherein said dielectricmaterial has a leakage current reduction that is about 10 or more afterlaser treatment.
 10. The dielectric film of claim 1 wherein saidreflectance spectra has about 60-70% reflectance at 248 nm after lasertreatment.
 11. An electronic structure comprising at least a dielectricmaterial comprising atoms of Si, C, O and H, said dielectric materialhaving a covalently bonded tri-dimensional network structure, adielectric constant of not more than 2.8 and an absorption spectra thatis substantially equivalent to SiO₂.
 12. The electronic structure ofclaim 11 wherein said covalently bonded tri-dimensional networkstructure comprises Si—O, Si—C, Si—H, C—H and C—C bonds.
 13. Theelectronic structure of claim 11 wherein said dielectric materialcomprises molecular scale voids of between 0.3 and 50 nm in diameter.14. The electronic structure of claim 13 wherein said molecular voidsoccupy a volume between 0.5% and about 50%.
 15. The electronic structureof claim 11 wherein said dielectric material comprises a crackpropagation velocity in water of less than 10⁻⁹ meters per second. 16.The electronic structure of claim 11 further comprising an underlyingsubstrate.
 17. The electronic structure of claim 16 wherein saidunderlying substrate comprises a semiconducting material, an insulatingmaterial, a conductive material or a combination, including multilayersthereof.
 18. The electronic structure of claim 17 wherein saidunderlying substrate comprises a semiconducting material.
 19. Theelectronic structure of claim 11 wherein said dielectric material has aleakage current reduction that is about 10 or more.
 20. The electronicstructure of claim 11 wherein said reflectance spectra has about 60-70%reflectance at 248 nm.